The amended, proposed research program is a basic science (non-clinical) evaluation of a significant ultrasound-induced biological effect which is intended to determine the current and future role of diagnostic ultrasound technology. The medical profession benefits if it can be shown that diagnostic ultrasound is a significant medical risk to the patient by advising clinicians about this risk, and suggesting how (through a possibly modified Mechanical Index) the clinician can monitor the degree of risk. Likewise, medical profession benefits if it is show that diagnostic ultrasound is not a significant medical risk to the patient by eliminating this as a clinical concern. In either case, there is clear medical significance. The data necessary to decide this issue is not currently available, but the current status regarding ultrasound-induced lung damage in experimental animals supports the view that diagnostic ultrasound equipment can damage human lungs. Most mammalian lungs, functionally are very similar and therefore, it is likely that lung damage and hemorrhage associated with ultrasound is related to structural differences that exists between species. Critical structural features of the lung that can be used to separate species into distinct groups are pleural thickness (thin verses thick), pleural blood supply (pulmonary artery verses bronchial artery), septal or interlobular connective tissue (scant verses abundant), and relative thickness of the chest wall (thin or thick [relative amounts of skin, muscle, fat, connective tissue]). On the basis of these comparisons, human beings can be clearly grouped with pigs (the "thick" group) and therefore, pigs will represent the animal model for understanding the pathogenesis of ultrasound-induced lung damage and hemorrhage in human beings. In addition, when these same comparisons are made between the "thick" group which contains human beings and pigs, and the "thin" group, it is clearly demonstrated that rats and rabbits are in the "thin" group. This latter group serves as a critical structural biologic control group to test the hypothesis that structural differences are truly the critical components that provide human beings with ample protection from any harmful bioeffects associated with ultrasound. The experimental (animal-based) research program has the four specific aims, viz. (1) to evaluate ultrasound levels at which minimum detectable lung hemorrhage occurs as a function of species, (2) and of age, (3) to evaluate functional alterations from ultrasound induced-lung hemorrhage at superthreshold conditions, and (4) to evaluate the damage mechanism of ultrasound-induced lung hemorrhage.